All the groups should be back by May 01st, May 05th at the latest if they instead head for another city to get back to Aqures Ixen (such as Balicea or Esdham). Most groups will be able to meet troops from Esdham and get their help once they get past the mountains closing off the southern half of the continent, or they'll get the help from Hypello if they go by sea and reach Balicea.